This invention relates generally to establishing telephone communications between a remote communications device and a local communications terminal. The invention is especially applicable for telephone communications between a central security monitoring facility at a remote location and a local security system terminal.
Many homes are now equipped with a local security system terminal which is capable of communicating with a central security monitoring facility over the telephone lines. In a typical operation, when an alarm condition occurs, a module in the local security system dials the telephone number of the central security monitoring facility, and generates an alarm in the computer of the central security monitoring facility, so that the central security monitoring facility can call the police, fire department, etc. for the owner. Many of the local security system terminals are also capable of receiving a telephone call from the central security monitoring facility for the purpose of checking on the status of the local security system terminal or sending control information to the local security system terminal. For this purpose, the local security system terminal is equipped with a ring answer circuit which is set to answer a telephone call after a certain number of rings (generally six to fifteen rings).
A problem has been presented for this security arrangement by the increased use of telephone answering machines. Typically these machines are set to answer the telephone after two to five rings. Thus, if the central security monitoring facility tries to call the local security system terminal, the telephone answering machine will answer before the telephone rings a sufficient number of times for the ring answer circuit of the local security system terminal to answer. Consequently, the telephone answering machine prevents the central security monitoring facility from gaining access to the local security system terminal.
The present invention solves this problem by providing a remote actuated command circuit which is designed to monitor the telephone line and to allow the central security monitoring facility to override and bypass the telephone answering machine. In particular, when the monitoring facility is calling and the telephone answering machine answers, a predetermined signal is sent from the monitoring facility onto the telephone line. This predetermined signal is sensed by the remote actuated command circuit, and the local security system terminal is thereupon connected to the telephone line so that the remote monitoring facility has seized the telephone line for data exchange or device control purposes without interference from the telephone answering machine.
In order to maintain tight controls on remote access to local security system terminals, the remote actuated command circuit of the present invention detects a predetermined signal which is not available to an ordinary telephone user. In a preferred embodiment, the remote actuated command circuit detects one or more of the four dual tone multi-frequency ("DTMF") tones that are not provided on a typical telephone keypad. Once detected, an output signal can be generated for overriding automatic telephone answering equipment and seizing the telephone line to establish communication between the remote monitoring facility and local security system terminal. The DTMF tones that are used in touchtone telephones include sixteen (16) tones. The normal telephone keypad uses only twelve of these sixteen tones. The unused tones have traditionally been utilized and reserved for routing a call through telephone switches. In other words, these tones are normally used only by the various telephone switching offices that cause a connection to be established between the calling and called parties and are not used once a connection has been established.
It is known to provide a telephone device with remote access capability through the use of predetermined codes or tones transmitted on the telephone line. One example includes the "beeperless remote" telephone answering machines. These devices enable an owner of a machine to call his home from a remote location and send a specific tone (e.g. press the "2" touchtone button on his telephone keypad) once the call has been established. This allows the owner to replay the messages that have been recorded, turn the answering machine off, reset the tape position where the next message is to be recorded, etc. Another example of a device actuated remotely by sensing predetermined codes or tones on the telephone line is disclosed in U.S. Pat. No. 4,584,434, where an answering machine is used to instruct a calling party to press a certain touchtone button if direct connection to a telecopier is needed.
These devices require that the code or tones be accessible to the ordinary telephone user--they use the twelve DTMF tones available on the normal telephone keypad. This approach is totally unsuitable for a security system where for security purposes it is essential to prevent unauthorized access to the local security system terminal.
With the foregoing in mind, it is a primary object of the present invention to provide a remote actuated command circuit which establishes telephone communications between a communications device at a remote location and a local communications terminal device without interference from a telephone answering machine connected to an incoming telephone line.
It is a further and more specific object of the present invention to provide a remote actuated command circuit which establishes these communications when it receives from the remote communications device a predetermined signal not normally available to a telephone user.